How Correct Are The Presidential Candidates On Big Scientific Issues?

From fracking to stem cell research, the answers may surprise you.

As the U.S. presidential election shifts away from primary races and toward the general election, it's important to take a critical look at what it is the candidates actually stand for. It's important for our leaders to be scientifically literate so they can make decisions based on facts and reason.

We've taken a look at the stances of Hillary Clinton (Democrat), Donald Trump (Republican), Gary Johnson (Libertarian), and Jill Stein (Green) to see how they align with the scientific evidence of six major issues this election season.

1. Climate Change

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Science: There is an overwhelming level of scientific agreement that climate change is real and that human activity is primarily responsible. Climate change will lead to rising sea levels, extinction of animals, droughts, and more. Scientists agree that we need to act and need to act now.

Johnson: (Agree, with provisions) While Johnson agrees that human-driven climate change is real, he does not support most government regulations to cut carbon emissions or tax subsidies for more sustainable energy sources.

Stein: (Agree) Stein has called for aggressive action to combat climate change, starting with calling a national state of emergency. She would end future fossil fuel initiatives and build up sustainable energy industries.

2. Fracking

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Science: Fracking is a method for extracting natural gas from shale far beneath the ground, freeing up a source that was previously off limits. There is a lot of controversy surrounding the practice, as the full environmental impact is not well understood. It has been linked to the contamination of groundwater in some cases, but when done properly, will not. According to the U.S. Geological Survey, earthquakes are not a serious risk from fracking.

Clinton: (Supports, with regulations) Clinton has historically supported fracking, but believes it should be restricted when local residents oppose it, methane contamination in the water or air is detected, if frackers are not forthcoming about the chemicals used during the process.

Trump: (Supports) Trump supports the use of fracking as an energy source and opposes government regulations that would impede production. Trump's stance on the issue is economic-based and he has not discussed the environmental impact.

Johnson: (Supports) Johnson has said he has "an open mind" toward fracking, but also has expressed concerns about contamination of groundwater.

3. Genetically Modified Organisms (GMOs)

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Science: Genetic modification gives scientists the ability to create crops that are larger and resistant to environmental factors like drought, making them an attractive option as the human population continues to grow and climate change makes growing conditions harsh. A 2014 metanalysis spanning 29 years and 1 trillion meals has found that GM crops are safe to eat, with the National Academy of Science finding similar results.

Clinton: (Agrees) Clinton supports modification of food, claiming that the problem lies with public perception, not evidence-based concerns about its safety. Clinton does support labeling of GMOs, but also believes they are safe and drought-resistant crops are necessary.

Trump: (Unclear) Trump has not said much on the issue. He did create a (now-deleted) tweet jokingly suggesting that GM corn "creates issues in the brain" to explain low poll numbers in Iowa, he also told the Iowa Farm Bureau that he supports biotech crops and opposes mandatory labeling.

Johnson: (Unclear) As Johnson suffers from Celiac disease and needs to be aware of what he's eating, he says he is very much in favor of comprehensive food labeling, including GMO. However, he has not commented on the safety of the crops themselves.

Stein: (Disagrees) Stein not only wants to label GMO food but has also proposed temporarily banning them.

4. Stem Cell Research

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Science:Stem cell research has the power to revolutionize modern medicine. Through the use of stem cells, there is the potential to grow replacement organs, treat neurodegenerative diseases, cure heart disease, and much more. It is possible to transform adult cells into stem cells, but the process is lengthy and the yield is too small to do experiments at the scale required. Sourcing the cells from embryos would be ideal, but there has been considerable pushback on the ethics of them.

Clinton: (Agrees) Clinton once said she would lift the ban on embryonic stem cell research and has stated that she would increase funding to the National Institutes of Health and National Science foundation in order to drive biomedical research forward.

Clinton: (Agrees) While Clinton was once skeptical of the (non-existent) link between vaccines and autism, she has more recently said that "the science is clear" and likened vaccine denial to the belief the Earth is flat.

Stein: (Agrees, with provisions) Stein, a physician, acknowledges the role immunizations have in improving public health, but she wants to remove corporate influence from the FDA, claiming there is a bias. For that reason, she also opposes mandatory vaccination.

Clinton: (Agree) During her 2008 bid for president, Clinton said that she supports NASA and would increase funding. Not only does she support robot and human spaceflight, but NASA's work involving Earth science and climate change.

Trump: (Disagree) While Trump has given theoretical support for NASA's initiatives, he would prefer for space exploration to become privatized.

Johnson: (Disagree) In order to decrease the federal budget, Johnson said he would cut NASA spending by 43 percent. He hopes that private companies would be able to make up for that difference.